import java.util.Stack;

class MyQueue {
    private Stack <Integer> stack1;
    private Stack <Integer> stack2;


    public MyQueue() {
        stack1=new Stack<>();
        stack2=new Stack<>();

    }
    
    public void push(int x) {
        stack1.push(x);
    }
    
    public int pop() {
        if(empty()){
            return -1;
        }else{
            if(stack2.empty()){
                while(!stack1.empty()){
                    int tmp=stack1.pop();
                    stack2.push(tmp);
                }
            }
           return stack2.pop();
        }
    }
    
    public int peek() {
        if(empty()){
            return -1;
        }else{
            if(stack2.empty()){
                while(!stack1.empty()){
                    int tmp=stack1.pop();
                    stack2.push(tmp);
                }
            }
            return stack2.peek();
        }
    }
    
    public boolean empty() {
        return stack1.empty()&&stack2.empty();
    }
}